Light guiding structure of a light guide plate

ABSTRACT

A light guiding structure of a light guide plate is provided. The light guiding structure comprises a plurality of protrusion ridge portions extending along a longitudinal direction. The height or the vertex angle of each protrusion ridge portion periodically or randomly varies along the longitudinal direction.

This application is a divisional application of U.S. application Ser.No. 12/470,650 filed May 22, 2009, which claims priority to TaiwanPatent Application No. 098103832 filed on Feb. 6, 2009, the disclosuresof which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides a light guiding structure of a lightguide plate. In particular, the present invention provides a lightguiding structure that shields defects.

2. Descriptions of the Related Art

Because of advantages such as low power consumption, light weight, lowemission and good portability, liquid crystal displays (LCDs) have beenwidely applied to TV sets, computer screens, notebook computers, vehiclenavigation systems, mobile communication devices and the like.Accordingly, LCDs have gradually replaced conventional displays and havebecome the mainstream product in the display market. One of the criticalcomponents in an LCD is the backlight module, which is responsible forsupplying uniform and sufficient light for the LCD panel.

Depending on the location where the light sources are disposed,backlight modules primarily comprise two categories: the direct-lighttype and the edge type. In the backlight module of the edge type, thelight source is disposed on one edge of the light guiding plate. Themost prominent advantage of the edge type is that the backlight moduleas a whole can be made to be light and thin, while the requirements ofhigh luminance, low cost and uniform brightness are still satisfied.Accordingly, the backlight modules of the edge type have drawn a lot ofattention in applications of specific LCDs sizes. In addition, the lightguide plate of the edge type backlight modules may be a flat plate orwedge plate, in which a single side can be provide with a light sourceor the light sources may be provided on both sides of the light guideplate to enhance the overall luminance.

However, local bright spots or dark spots resulting in non-uniformityare likely to occur in the surface light source projected by theemergent surface of the light guide plate. For example, local brightspots may be caused by some missing structures during the productionprocess of the light guide plate, and local dark spots may be caused byscratching during the transport process. A conventional solution is toadditionally provide a lower diffusion sheet to mitigate the effect ofbright spots or dark spots. Unfortunately, the disposition of the lowerdiffusion sheet tends to cause degradation of the overall luminance. Onthe other hand, without the lower diffusion sheet, the defects of brightspots or dark spots cannot be mitigated, and this is undesirable for theoverall uniformity of the surface light source.

In view of this, it is highly desirable in the art to provide a lightguiding structure of a light guide plate which eliminates the need of anadditional lower diffusion sheet while eliminating the problem of brightor dark spots and scratching.

SUMMARY OF THE INVENTION

One objective of this invention is to provide a light guiding structureof a light guide plate, which is adapted to shield defects such asbright or dark spots on the light guide plate by disordering light pathsthrough the structural variations of the light guiding structure.

This invention discloses a light guiding structure of a light guideplate. The light guiding structure comprises a plurality of protrusionridge portions extending along a longitudinal direction. Each of theprotrusion ridge portions has a height having a height variation and anaverage height corresponding thereto along the longitudinal direction.The height variation is between 2% and 15% of the average height. Inanother embodiment of this invention, each of the protrusion ridgeportions has a vertex angle having an angle variation and an averageangle corresponding thereto along the longitudinal direction, whereinthe angle variation is between ±10% of the average angle.

The detailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a light guiding structure according to thefirst embodiment of this invention;

FIG. 2 is a schematic view of a light guiding structure according to thesecond embodiment of this invention;

FIG. 3 is a schematic view of a light guiding structure according to thethird embodiment of this invention; and

FIG. 4 is a schematic view of a light guiding structure according to thefourth embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following descriptions, this invention will be explained withreference to embodiments thereof. However, these embodiments are notintended to limit this invention to any specific environment,applications or particular implementations described in theseembodiments. Therefore, descriptions of these embodiments are only forpurposes of illustration rather than limitation. It should beappreciated that in the following embodiments and the attached drawings,dimensions of the elements are only depicted to clearly disclose thesubject matter of this invention but not to limit this invention, andelements unrelated to this invention are omitted from depiction.

FIG. 1 depicts a light guide plate 2 according to a first embodiment ofthis invention. The light guide plate 2 comprises an emergent surface25, a bottom surface 26 opposite the emergent surface 25 and an incidentsurface 27 located on the side edge thereof. The incident surface 27 isadapted to receive incident light from a light source 29. In thisembodiment, the emergent surface 25 of the light guide plate 2 is formedby a light guiding structure 20. The light guiding structure 20comprises a plurality of protrusion ridge portions 21, each of whichsubstantially extends along a longitudinal direction X perpendicular tothe incident surface 27, and the protrusion ridge portions 21 define theemergent surface 25.

The feature of the light guiding structure 20 is that each of theprotrusion ridge portions 21 varies along the longitudinal direction X.In this embodiment, each of the protrusion ridge portions 21 has asubstantially triangular cross section and a height H. Each of theheights H of the protrusion ridge portions 21 exhibits a heightvariation along the longitudinal direction X.

More specifically, as the height H of each protrusion ridge portion 21varies along the longitudinal direction X, an average height may bedefined for each of the protrusion ridge portions 21. Preferably, thevariation of the height H ranges between 2% and 15% of the averageheight. Additionally, if the height H varies periodically, the variationperiod of the height H preferably ranges between 40 times and 70 timesof the height variation.

In this embodiment, each of the protrusion ridge portions 21 with atriangular cross section may have a vertex angle θ, which preferablyranges between 60 degrees and 170 degrees, and even better, between 70degrees and 110 degrees. The protrusion ridge portions 21 may haveidentical or different vertex angles θ (e.g., randomly or regularlyvarying angles). The vertex angles θ of the protrusion ridge portions 21depicted in FIG. 1 are substantially identical to each other, but thisis only for purposes of illustration rather than limitation.Additionally, the protrusion ridge portions 21 depicted in FIG. 1 areadjacent to each other and continuously distributed on the light guideplate 2.

Although the protrusion ridge portions 21 disclosed in this embodimentare disposed on the emergent surface 25, the protrusion ridge portions21 may also be disposed on the bottom surface 26. In other embodiment,the emergent surface 25 is formed with the protrusion ridge portions 21,while the bottom surface 26 may be formed with a sandblasting structure(not shown) or a conventional V-shaped groove. Alternatively, the bottomsurface 26 may be formed with the protrusion ridge portions 21, whilethe emergent surface 25 may be formed with the sandblasting structure(not shown) or the conventional V-shaped groove instead.

It should be noted that the light guide plate in this invention is notlimited to a flat plate or a wedge plate. The height variation of theprotrusion ridge portions 21 may also be either periodic or random.However, if the protrusion ridge portions 21 have a short heightvariation period, it can easily gain a better result of disorderinglight rays and thereby get a better effect of shielding bright or darkspots.

A second embodiment of this invention is depicted in FIG. 2. On basis ofthe first embodiment, the vertex angles θ vary among the protrusionridge portions 21, and the protrusion ridge portions 21 are periodicallydistributed on the light guide plate 2 according to the vertex angles θ(i.e. θ₁, θ₂, θ₃). As shown in FIG. 2, the vertex angles θ varycyclically in the order of a first angle θ₁, a second angle θ₂ and athird angle θ₃. For example, the first angle θ₁ is 80 degrees, thesecond angle θ₂ is 120 degrees and the third angle θ₃ is 150 degrees; oras another example, the first angle θ₁ is 120 degrees, the second angleθ₂ is 150 degrees and the third angle θ₃ is 160 degrees. It should benoted that the angle variations and the number of angles in thevariation cycle described above are only provided for illustration butnot for limitation, and can be devised depending on the demands of theproduct.

A third embodiment of this invention is shown in FIG. 3. As shown, theprotrusion ridge portions 21 are distributed on the light guide plate 2and spaced apart from each other. Additionally, both the variation rangeand whether the vertex angles θ (i.e. θ₁, θ₂, θ₃) vary or not are justsimilar to what is described in the above embodiments and will not bedescribed again herein.

A fourth embodiment of this invention is shown in FIG. 4. Unlike theabove embodiments, the vertex angle θ₄ of the protrusion ridge portions21 in this embodiment exhibits an angle variation along the longitudinaldirection X. In more detail, as the vertex angle varies, an averageangle may be defined for the vertex angle θ₄ of each of the protrusionridge portions 21. Preferably, the angle variation of the vertex angleθ₄ ranges between ±10% of the average angle. The angle variation may beperiodic or random. If the angle variation is periodic, the periodpreferably ranges between 10 times and 50 times of the angle variation.

It should be noted that the protrusion ridge portions 21 may bedistributed continuously or spaced apart discontinuously. The vertexangles θ₄ can not only vary periodically or randomly along thelongitudinal direction X, they can further be identical to or differentfrom each other (e.g., distributed randomly or periodically). This hasalready been disclosed in the above embodiments and will not bedescribed again herein.

According to the above descriptions, the light guiding structure of thisinvention has a height or vertex angle thereof varied periodically alongthe longitudinal direction and has protrusion ridge portions arranged invarious ways, so that the light paths are interfered to result avisually disordering effect. Thereby, the defects of bright spots, darkspots or scratches can be shielded and the product yield can beimproved.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

1. A light guiding structure of a light guide plate, comprising: aplurality of protrusion ridge portions extending along a longitudinaldirection, in which each of the protrusion ridge portions has a vertexangle having an angle variation and an average angle correspondingthereto along the longitudinal direction; wherein the angle variation isbetween ±10% of the average angle.
 2. The light guiding structure ofclaim 1, wherein the light guide plate has an incident surfacesubstantially perpendicular to the longitudinal direction.
 3. The lightguiding structure of claim 2, wherein the angle variation is aperiodical variation.
 4. The light guiding structure of claim 3, whereinthe angle variation varies with a period between 10 times and 50 timesof the angle variation.
 5. The light guiding structure of claim 2,wherein the angle variation is a random variation.
 6. The light guidingstructure of claim 4, wherein each of the protrusion ridge portions hasa cross-section which is substantially a triangle.
 7. The light guidingstructure of claim 6, wherein the protrusion ridge portions areperiodically distributed on the light guide plate according to thevertex angles.
 8. The light guiding structure of claim 7, wherein thevertex angles are between 60 degrees and 170 degrees.
 9. The lightguiding structure of claim 8, wherein the vertex angles are between 70degrees and 110 degrees.
 10. The light guiding structure of claim 7,wherein the protrusion ridge portions are mutually adjacent andcontinuously distributed on the light guide plate.
 11. The light guidingstructure of claim 2, wherein the light guide plate has an emergentsurface substantially defined by the protrusion ridge portions.
 12. Thelight guiding structure of claim 11, wherein the light guide platefurther comprises a bottom surface opposite to the emergent surface, anda sandblasting structure is formed on the bottom surface.
 13. The lightguiding structure of claim 2, wherein the light guide plate comprises anemergent surface and a bottom surface opposite to the emergent surface,and the bottom surface is substantially defined by the protrusion ridgeportions.
 14. The light guiding structure of claim 13, wherein asandblasting structure is formed on the emergent surface.
 15. The lightguiding structure of claim 2, wherein the light guide plate is one of aflat plate and a wedge plate.